/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.iotdb.db.rescon;

import org.slf4j.Logger;

import java.util.concurrent.*;

public abstract class AbstractPoolManager {

    private static final int WAIT_TIMEOUT = 2000;

    protected ExecutorService pool;

    /**
     * Block new flush submits and exit when all RUNNING THREADS AND TASKS IN THE QUEUE end.
     */
    public void close() {
        Logger logger = getLogger();
        pool.shutdownNow();
        long totalWaitTime = WAIT_TIMEOUT;
        logger.info("Waiting for {} thread pool to shut down.", getName());
        while (!pool.isTerminated()) {
            try {
                if (!pool.awaitTermination(WAIT_TIMEOUT, TimeUnit.MILLISECONDS)) {
                    logger.info("{} thread pool doesn't exit after {}ms.", getName(), +totalWaitTime);
                }
                totalWaitTime += WAIT_TIMEOUT;
            } catch (InterruptedException e) {
                logger.error("Interrupted while waiting {} thread pool to exit. ", getName(), e);
                Thread.currentThread().interrupt();
            }
        }
    }

    public synchronized Future<?> submit(Runnable task) {
        return pool.submit(task);
    }

    public synchronized <T> Future<T> submit(Callable<T> task) {
        return pool.submit(task);
    }

    public int getWorkingTasksNumber() {
        // in ITs, pool may be closed and therefore pool will be null
        if (pool == null) {
            return 0;
        }
        return ((ThreadPoolExecutor) pool).getActiveCount();
    }

    public int getWaitingTasksNumber() {
        // in ITs, pool may be closed and therefore pool will be null
        if (pool == null) {
            return 0;
        }
        return ((ThreadPoolExecutor) pool).getQueue().size();
    }

    public int getTotalTasks() {
        return getWorkingTasksNumber() + getWaitingTasksNumber();
    }

    public int getCorePoolSize() {
        if (pool == null) {
            return 0;
        }
        return ((ThreadPoolExecutor) pool).getCorePoolSize();
    }

    public abstract Logger getLogger();

    public abstract void start();

    public void stop() {
        if (pool != null) {
            close();
            pool = null;
        }
    }

    public abstract String getName();
}
